The basic elements of most present day fiber optic cable are four in number: (1) a strength member; (2) a plurality of tubes disposed on and around the outer periphery of the strength member; (3) optical fibers in the tubes; and (4) a sheath or jacket circumscribing the tubes. In some optical cable designs, the tubes are divided into groups, one group of tubes containing fibers (system fibers) intended to be used for transmission purposes (transmitting and receiving) and another group of tubes contain fibers that are intended to be used as spares (protection spares, assigned spares for a given and identified transmission system). Usually the tube containing the system (working) fibers has a color code that identifies it with a tube containing the assigned spares so that they may be physically related one to another. Due to such an arrangement, any outage or failure of a transmission path arising out of a failure of a transmission fiber can be repaired by using one or more of the fibers in the assigned spares tube. When the original tranmission path is repaired, the spare is disconnected (deactivated) and resumes its "spare" function. This switching back and forth between the system fibers and their associated spares is accomplished automatically by prior art switching devices.
Even though a tube which carries system fibers is color coded to identify a given assigned spares tube associated therewith, when the jacket of prior art optical fiber cable is split opened to expose the tubes (both system tubes and assigned spares tubes), there is a propensity for the system tubes to become physically separated from its corresponding spares tubes; thus, the possibility of error creeps in the selection of the right color coded tube and its associated assigned spares tubes notwithstanding that such tubes (transmission/spares) are adjacent one to another in the as manufactured cable structure.
It is towards the solution of this problem that the present invention is directed.